MAINTENANCE MANAGEMENT ANALYSIS OF INDUCE DRAFT FAN (IDF) EQUIPMENT OF COAL FIRE POWER PLANT (CFPP) LONTAR USING LIFE CYCLE COST ANALYSIS APPROACH

To maintain the performance to optimalization operating at Coal Fire Power Plant (CFPP) the reliability of power plant equipment needs to be maintained especially on critical equipment. Based on CFPP failure data during 2012 – 2017, one of the critical equipment is the Induce Draft Fan (IDF). The Journal will analyse the reliability, availability and maintainability for the IDF equipment with the approach of Life Cycle Cost Analysis (LCCA). Using the IDF equipment failure data during 2012 - 2017 which is processed using Minitab 17 application with Weibull Analysis method, the results obtained the mean value (µ) for MTTF and shape parameters (β) and scale parameters (η) for calculation MTTR. That data combined with the hours of annual routine maintenance periods for each unit, used to calculate the operating and maintenance (O&M) hours of IDF in a year and then combined with operational cost data so the total O&M costs for the IDF during 15 years period obtained. Consider with assumptions for the calculation, the final results can provide input for management to making appropriate maintenance decisions. The results of LCCA approach for 15 years obtained the lowest total maintenance cost is IDF unit 1 of 527.68 billion.


INTRODUCTION
To meet the growing needs for electricity in Indonesia, the government issued a policy of the 10,000 MW Fast Track Program Phase 1 (FTP-1). To achieve the energy needs in 2008 the government began to build power plants program and it is expected that the power plants will be ready to operate in 2009 (Admin, 2008).
Lontar CFPP is the one of the government Fast Track Program power plants that uses coal as the main fuel. At the coal fire power plant, coal is burned to heat the water in the boiler pipe until it turns into steam with a certain pressure. In the coal combustion process the air pressure is maintained at certain set points (under atmospheric pressure). To maintain the set-point, the combustion system is equipped with Force Draft Fan (FDF) and Induce Draft Fan (IDF) equipment. Under these conditions the reliability of the FDF and IDF equipment becomes very critical because if there is interference with the equipment it will have an impact on the loss of production opportunities.
In the CFPP generating system, IDF equipment is included in the Boiler Air and Gas System. The failure data equipment of Lontar CFPP from 2012 -2017 as shown in Figure 1, Boiler Air and Gas System are in the top 5 causes of loss production, so to reduce the loss of production in the Boiler Air and Gas System in the next period the reliability of IDF equipment needs to be optimized. To maintain the reliability of the IDF equipment, maintenance must be optimal. In the study (Wardoyo, 2017) applying periodic maintenance interval optimization based on an analysis of Reliability, Availability and Maintainability (RAM) in the Saguling Hydroelectric Power Plant, while (Nugraha, Silalahi, & Sinisuka, 2016) implemented Reliability, Availability, Maintainability and Security (RAMS) for maintenance of 150-kV Power Transmission Submarine cables. (Bhakti & Kromodihardjo, 2015) designed a maintenance system using the Reliability Centered Maintenance method on medium pulverized (Eliyus, Alhilman, & Sutrisno, 2014) to estimate maintenance costs and determine machine life and number of maintenance personnel using the Life Cycle Cost method and (Madiyansah, 2018) conduct an economic analysis on the pulverizer equipment at the power plant with the Life Cycle Cost Analysis approach.
There is still not much research for the reliability of IDF equipment. Therefore, researchers try to make a study of the reliability, availability and maintainability for the Induce Draft Fan (IDF) with a Life Cycle Cost Analysis (LCCA) approach. The final result of this analysis is to provide an input to management for making appropriate decisions in optimizing the maintenance costs of Induce Draft Fan (IDF) equipment.

RESEARCH METHOD
This research was conducted with literature studies and field studies to determine the condition of the Induce Draft Fan (IDF) equipment in the Lontar CFPP so that data obtained for research from the year of operation during 2012 to 2017, then the data is processed using Minitab 17 application with Weibull analysis until we get the value of shape parameter (β), scale parameter (η) and mean (µ).
From the above parameters then used to calculate the Mean Time to Failure (MTTF) and Mean Time to Repair (MTTR) values for each IDF equipment. The data processing then performed to calculate the costs for each IDF equipment's in accordance with the life cycle cost analysis (LCCA) approach to obtain the total value of the operating and maintenance costs for the IDF equipment's during the operating period. From the total cost, it is obtained that the most optimal Maintenance Management between each IDF equipment by considering the assumptions that exist. The research can be described as shown in Figure 2. Generally, Life-Cycle Cost (LCC) is the total cost during an asset operating from research, planning, design, testing, production processes, certification, operation, maintenance, until disposal of asset. The general formula for calculating the Life Cycle Cost for an equipment/ system can be formulated as follows: ( From the above data then processed to get the MTTF value on each unit of IDF equipment using Minitab 17 software. In this study the distribution analysis used is Weibull Analysis. From the results of the software analysis, the data for each IDF equipment obtained as follows: (1) Problem Identifications -Failure Data of Equipment -Pareto Loss of Equipment From the simulation results of the IDF equipment using software, the value is obtained shape parameter (β), scale parameter (η) and mean (µ) which can be recapitulated in

The Calculation of Mean Time to Repair (MTTR)
The time data used to repair IDF equipment during the specified period is summarized in table 3 as follows: From the above data then processed to get the MTTR value on each unit of IDF equipment using Minitab 17 software. In this study the distribution analysis used is Weibull Analysis. From the results of the software analysis, the data for each IDF equipment obtained as follows: From the simulation above obtained data shape parameter (β) and scale parameter (η)

Cost Analysis a. Investment Cost (CI)
The initial investment costs for processing the initial contract data during the construction of the plant for the installation for unit #1 of IDF equipment can be calculated as follows:

b. Operational Cost (CO)
Operating Costs are routine operating costs occurred in accordance with operating hours reduced by annual routine maintenance hours according to the power plant maintenance cycle. One unit consists of 2 IDF equipment so each IDF equipment operates 50% of the maximum capacity of the equipment. The operational cost analysis for 1 IDF machine is as follows: Power Consumption(a) = 215 kW Operating efficiency(b) = 50% Electricity cost (c) = 680 (Rp/kWh) Hourly production costs per unit = Rp. 4,386 million

c. Maintenance cost (CM)
Maintenance costs are routine maintenance costs occurred every year to maintain the performance of IDF equipment in normal conditions. Routine maintenance schedule (periodic inspection) for each unit in table 6 as follows: SPEKTRUM INDUSTRI e-ISSN : 2442-2630Vol. 18, No. 2, Oktober 2020p-ISSN : 1963   The maintenance costs for each work each IDF equipment are as follows:    e-ISSN : 2442-2630Vol. 18, No. 2, Oktober 2020p-ISSN : 1963

d. Failure Cost (CF)
Represents the costs occurred to repair damage that occurred on the IDF machine in each unit during 15 years' operation. From the simulation results of MTTF calculations for each IDF equipment, an estimated time of the damage occurrence for each IDF equipment was obtained. Then from the time of the incident the simulation of the damage event time was carried out for 15 years to obtain the damage event for 15 years as shown in table 12.

Year -Total
From table 18, a simulation of the total cost of the unit 1 IDF equipment for 15 years is Rp. 532.70 billion, assuming the selling price of electricity is 1,352 Rp / kWh, the electricity sales for 15 years is 1,023.77 billion. Assuming the bank interest rate in 2017 is 10%, the NPV value = 247.14, then IRR = 5.64 and B / C = 76.43. From the LCC analysis results of the IDF equipment's in unit 1, unit 2 and unit 3 then recapitulated in table 19.

CONCLUSIONS
From the qualitative data analysis with Life Cycle Cost calculation for 15 years the lowest total cost is IDF unit 1 of 527.68 billion then IDF unit 2 of 532.42 billion and IDF unit 3 of 532.7 billion. From the above calculation with the same periodic maintenance cycle (SI-ME-SI-SE) for each unit, the total cost of maintaining an IDF equipment's for each unit for 15 years is different. The lowest total maintenance costs are on IDF unit 1. For the optimal maintenance cost, we recommended to simulate the equipment failure using data IDF unit 1 to prepare the predictive and preventive maintenance for each IDF unit then we can immediately anticipate the equipment failure with spare part preparation and quick equipment repair.